The present invention relates to a process for preparing legumes exhibiting reduced flatulence when digested by mammals and a process for reducing flatulence in legumes when digested by mammals and the products thus prepared.
Legumes are important foodstuffs and are likely to become more so in the future. For example, many legumes, especially those in some of the legume genuses, such as Phaseolus, Soja and Lens, are high in protein and provide an inexpensive alternative to animal protein.
Unfortunately, ingestion of some of the most nutritious and abundant legumes can be accompanied by severe flatulence as well as abdominal distress and poor digestibility. More specifically, the flatulence results in discomfort, diarrhea, loss of appetite, and poor growth, all of which have prevented the wide-scale use of these vegetable nutrients.
It is believed that the flatulence is due to various factors. For example, it has been postulated that the flatulence is attributable to the indigestibility by mammalian digestive enzymes of the flatulence-causing alpha oligosaccharides, such as raffinose, stachyose, and verbascose, and the like, present in legume products. The generally accepted explanation of the action of the alpha oligosaccharides in producing flatulence is that the enzyme alpha galactosidase, which hydrolyzes the xcex1-oligosaccharides, is not present in the intestinal tract of mammals. Thus, these compounds are not hydrolyzed and dissolved in the digestive tract so that they can be absorbed. Instead, they reach the lower intestine essentially intact. Here, anaerobic bacteria ferment these sugars with the resultant production of carbon dioxide, hydrogen, and methane gases, thereby producing flatus.
However, these xcex1-oligosaccharides are believed not to be the only source present in the legume that causes flatulence. It has been reported that flatulence is also due to components present in the cell wall fiber constituents. Others have conjectured that undigested starch and protein in the legumes are contributing factors to flatus production.
Various solutions have been proposed to reduce flatulence in legumes, but many of these focus on just one of the factors described herein above, viz., the flatulence-causing oligosaccharides. More specifically, many proposed solutions relate to the use of enzymes to enhance the digestibility of the oligosaccharides. Thus, one solution is to add oligosaccharide-digesting enzymes to the legume itself or as a food supplement to be ingested substantially simultaneously with the ingestion of the legume. For example, U.S. Pat. No. 3,632,646 to Sherba discloses the addition to foodstuff, such as legumes, of xcex1-galactosidases or other enzyme preparations capable of hydrolyzing the 1,6-linkages of stachyose and other food containing flatulence-causing polysaccharides. U.S. Pat. Nos. 4,376,127 and 4,376,128 to Lunde disclose a process of improving the digestibility of legumes and reducing the flatulence thereof by adding an enzyme system found in pineapple and papaya to the legumes prior to cooking said legumes. U.S. Pat. No. 5,651,967 to Rohde, Jr., et al. discloses a food supplement comprising a beta- fructofuranosidase which is alleged to enhance the digestibility of sugars and reduce flatulence. U.S. Pat. Nos. 5,445,957 and 5,651,967 disclose a food supplement to be ingested simultaneously with the legume comprising a beta- fructofuranosidase enzyme, a cellulose enzyme and a hemicellulose enzyme which together alleviate gastrointestinal distress caused from the digestion of legumes.
Another solution is leaching the oligosaccharides from the legumes. For example, one method is to soak the legume product in water. Sometimes, the soak is in hot water that gradually cools as the soaking progresses. The soaking water may or may not be changed with fresh water. By this method, it has been found that soaking significantly decreases the xcex1-galactoside content in lentils. (See, Frias, et al, Journal of Food Protection, 1995, 58, 692-695.) In addition, it has been found that cooking, by either boiling or pressure cooking, also decreases the xcex1-galactoside content. (See, Vidal-Valverde, et al., Journal of American Dietetic Association, 1993, 93, 547-550).
Industrial soaking, which can be used to leach the oligosaccharides from the legumes, falls into two main processes. The most practiced is an ambient or initially warm soak that is allowed to cool naturally for several hours, followed by a very short blanch at typically 180xc2x0 F. The high controlled temperature blanch is used to optimize initial rehydration, deaerate the legumes and coagulate the protein to prevent starch leaching out of the legumes during cooking.
A second industrial process is to use multiple short soak times at temperatures sufficient to accelerate the rehydration process. In this process, the legumes are heated in a series of blanchers.
Other methods utilized and/or proposed to reduce flatulence include dehulling of the bean (See U.S. Pat. No. 202,975); fermenting the legume with a microbe (See, Goel, et al., Indian J. Nutr. Dictet, 1980, 18, 215-217); and germinating the legume (See, e.g., Rao, et al. J. Agric Food Chem., 1978, 26, 316-319). In fact, Rao, et al. in Journal of Food Science, 1983, 1791-1795 disclose that xcex3-irradiation is effective for elimination of flatulence-causing oligosaccharides in legumes during germination.
In the Ph.D. thesis of Matrid King from the University of Arkansas (1987), the use of endogenous xcex1-galactosidase in cowpeas was explored for the purpose of removing the flatulence-causing oligosaccharides therefrom. For example, soaking, germination, and fermentative and non-fermentative incubation treatments for stimulating xcex1-galactosidase hydrolysis of the oligosaccharides were investigated. The thesis disclosed that the enzyme activity of the xcex1-galactosidase increased until a temperature maximum of 113xc2x0 F. was obtained, i.e., above this temperature the enzyme activity decreased. For example, a two minute incubation at 50xc2x0 C. (122xc2x0 F.) 55xc2x0 C. (129xc2x0 F.) and 60xc2x0 C. (140xc2x0 F.) resulted in a 50, 70 and 90% loss of activity compared to the activity at 113xc2x0 F. In addition, King disclosed that endogenous xcex1-galactosidase has maximum enzymatic activity at a pH ranging between 4.0 and 5.0.
Although these methods described hereinabove may be useful in reducing flatulence caused by oligosaccharides, these methods have not been successful in substantially removing the flatulence-causing oligo-saccharides from the legumes. In addition, these methods have ignored the flatulence caused by other components of the legumes. It has been suggested by researchers, however, that, at least with beans, oligosaccharides account for only about ⅓ of the cause of flatulence, and that ⅔ is caused by other components such as, e.g., undigested starch in the bean. Other research indirectly suggests that the sugars are responsible for the violent xe2x80x9cepisodesxe2x80x9d that occur approximately within five hours after ingestion of the legume, while xe2x80x9cbackground flatulencexe2x80x9d, which occurs regularly over a six to eight hour period after eating, is caused by the non-digested starch. Unfortunately, very little research, in comparison, has been directed to reducing the flatulence caused by these other components.
Recently, Yansoo Chung, in his Ph.D. thesis from Michigan State University (1996), reported that cooking whole navy beans for 10 minutes caused starch crystallization within the cell wall of the navy beans, thus impeding and preventing the digestive enzymes in the stomach from digesting (hydrolyzing) the starch.
Therefore, additional investigations are required to find the appropriate conditions to prevent such crystallization from occurring and thereby enhance the digestibility of these starches in the bean.
To date, no one has found a means to effectively reduce the flatulence caused by the digestion of legumes and thus, legumes, such as beans, remain unappealing to many consumers.
The present inventors have found such a solution. More specifically, they have found a means of significantly reducing the flatulence of legumes.
The present invention is directed to a process for reducing the flatulence caused by the digestion of the legume in mammals, which process comprises:
(1) soaking a legume in a water bath in stagnant, sprayed or flowing water at a first temperature which is at or above ambient temperature and below the critical rehydration temperature of the legume under conditions effective and for a period of time sufficient to produce a rehydrated legume having a moisture content which is at least 50% of a fully hydrated legume;
(2) soaking and heating the rehydrated legume of step (a) to a second temperature at a pH ranging from about 5.5 to about 9.0 under conditions effective to diffuse the flatulence-causing oligosaccharides from the legume to the soak water and to permit the naturally occurring oligosaccharide reducing enzyme present in the legume to digest the remaining flatulence-causing oligosaccharides in the legume to produce a legume that has substantially all of the flatulence-causing oligosaccharides removed therefrom, said second temperature being greater than the critical rehydration temperature and said first temperature and less than the inactivation temperature of said enzyme;
(3) heating the product of step (2) in a water bath to a third temperature under conditions effective and for a time sufficient to initiate gelatinization of starch present therein, said third temperature being greater than the first and second temperatures and the inactivation temperature of said naturally occurring oligosaccharide reducing enzyme, but less than the temperature to substantially coagulate the protein surrounding the starch granules in said legume; and
(4) optionally blanching the product of step (3) at a fourth temperature under effective blanching conditions, said fourth temperature being greater than the first, second and third temperatures.
The present invention is also directed to the preparation of a legume exhibiting reduced flatulence when digested by a mammal, which comprises repeating steps (1)-(3) hereinabove, and optionally step (4) and then
(5) mixing the legume thus treated with a food acceptable vehicle to form a legume-based mixture; and
(6) treating the product of step (5) under the desired preservation methods.
The present invention is also directed to the product thus formed by the processes described hereinabove.